Compressor unloading mechanism



Sept. 19, 1950 c. R. NEESON 2,522,762

COMPRESSOR UNLOADING MECHANISM Filed Nov. 15, 1947 2 Sheets-Sheet 1 INV EN TOR.

Czar/es Neesorz.

morn/rm.

Sept. 19, 1950 c. R. NEESQN 2,522,762

courasssoa momma uzcumsu Filed Nov. 15, 1947 2 Sheets-Sheet 2 BY WWW Patented Sept 19, 1950 COMPRESSOR UN LOADING MECHANISM Charles R. Neeson, Dayton, Ohio, assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Application November 15, 1947, Serial No. 786,273

Claims.

This invention relates to means for unloading individual cylinders of a' motor driven multicylinder refrigerant compressor under selected conditions to prevent overloading of the motor.

The pressure existing on the suction side of a refrigerant compressor provides an indication of the load existing on the refrigerant system as an incident to the room and evaporator coil temperatures existing at that time. When this provide an improved apparatus which may be associated with the unloader mechanism of individual compressor cylinders to unload these cylinders when predetermined compressor suction pressures are exceeded.

It is a further object of the invention to provide apparatus which may be associated with the unloader mechanism of individual compressor cylinders to unload these cylinders when pressure is high the work required to compress predetermined motor temperatures are exceeded. a given volume of refrigerant is high. A means e appa tus to be described herein is to prevent overloading of the motor driving the d p e pp the unloading pparatus compressor is provided by apparatus to unload described in my Patents No. 2,185,473 and individual cylinders of the compressor and there- 2,369,841 and reference may be had thereto for by reduce the volume of refrigerant compressed a o d a d description of a apparatus until its pressure lowers sufficiently to permit Which will be briefly referred to herein. the volume of refrigerant handled by the com- Other objects and advantages will become pressor t be increa ed, more apparent from the following. description It is a principal object of this invention to taken in Connection With t c p y combine means to unload some cylinders of a drawings. in which: multi-cylinder compressor in response to high Fig. 1 is a side elevation of a refrigerant comsuction pressure thereof with means to unload D e c pl to a l; additional cylinders of the compressor in re- Fig. 2 is a vertical section taken through the sponse to overheating of the motor driving the compressor of Fig. 1; compressor. The suction pressure responsive Fig. 3 is a section on the line 3-3 of Fig. 2; unloading apparatus is capable of determining and that a predetermined number of cylinders should Fig. 4 is a sectional view of appara adapted be unloaded for a given suction pressure. Howto unload compressor cylinders in response to ever, the length of time that the compressor motor temperature. must operate under abnormal pressure condi- 1:0 In Fig. 1 a motor compressor set incorporating tions is a factor which has heretofore been my invention is illustrated. A compressor [0 is ignored by unloader mechanisms. While operauppor by a base 2 n adapted o be driven tion of the compressor with a given number of by an electric motor I4. The armature ll; of cylinders unloaded might prevent the motor from o or I4 s Co p e to the main shaft I8 of the being injuriously overloaded this may only be compressor. The compressor is illustrated in true if the pressure drops within a reasonable more detail in Fig. 2 and a substantial portion of length of time. Therefore, I have provided its construction and attachments are as demeans responsive to motor temperature to unscribed in my Patent e co load additional cylinders when the motor tempr s r ill r te in Fi 2 mpri a hou perature becomes excessive. This combined with ng 20 provided with a bearin 22 in ch the a suction pressure. responsive unloader mechashaft i8 is journaled. A conventional seal 24 nism provides a more accurate control of the may b p y tw n the shaft l8 and housvolume of refrigerant handled by the compressor ing 20 in order to prevent the escape of refrigerthan has heretofore been obtainable and proant from the compressor housing. vides an adjustment of this volume in relation The shaft I8 includes a pair of counterbalances to rate of pressure drop. 26 and 28 which are located thereon and which It is a further object of this invention to protend to smooth vibration by acting as flywheels. vide mechanisms which may be associated with The front end of the shaft beyond the bearindividual cylinder unloading apparatus withing 22 is provided with a crank pin 30 which is out requiring that an entirely new unloading surrounded by a bearing ring 32 forming the apparatus be substituted .in a compressor to bearing surface for a plurality of piston rods 34. obtain the added features of unloading in re- The number of piston rods corresponds to the sponse to excessive suction pressure and motor number of cylinders in the compressor. The overheating. weight of the crank pin is counterbalanced by a balance weight 38.

It is an additional object of the invention to Each piston rod 34 extends radially towards its associated cylinder 38. The cylinders are radially, equally spaced about the center lines of the compressor. Each cylinder is offset longitudinally of the compressor by an amount equal to the distance between centers of the piston rods 34. Each cylinder comprises a liner 40 which is inserted through the outer end of the cylinder when a cylinder head 42 is removed. A suction manifold 44 surrounds the liners and communicates with a refrigerating system (not shown) through a suction port provided in the housing 20 and not illustrated herein. The suction manifold 44 communicates with the interior 48 of the compressor housing through a plurality of openings 48. The suction manifold is also in communication with the interior of the rear or right hand portion of the compressor of Fig. 2 through one or more openings 50. The entire interior of the compressor is therefore subjected to pressure equal to the suction pressure of the refrigerating system with which it is associated.

The refrigerant entering the compressor through the suction manifold 44 is admitted to each cylinder space through suction valves 52. The gas is admitted upon raising of the suction valve 52 and discharged from the cylinder upon the raising of a discharge valve 54. The details and operation of the piston, seal, liner and valve assembly are more fully set forth in my Patent 2,137,965 dated November 22, 1938. Discharge ports 58 are associated with each cylinder. Each of the discharge ports 58 extends through the main housing 20 and passes from the compressor through a main discharge port 60.

As described in Patent No. 2,185,473, a means for producing oil pressure is provided at 62. Oil pressure produced is used to lubricate moving parts of the compressor and to operate an unloader mechanism to be described. A master valve 64 is associated with the unloader mechanism and is adapted to control the delivery of oil pressure to unloader mechanisms associated with each compressor cylinder. Oil is delivered under pressure from means 62 to master valve 64. A plurality of tubes 66 connect the master valve 84 to individual unloader mechanisms associated with each compressor cylinder. One such unloader mechanism is illustrated in Fig. 2 and comprises a passage 68, a bore I and a piston I2 contained in the bore and urged toward the left in Fig. 2 by a spring I4. The strength of spring I4 is such as to be overcome by the pressure of the oil from means 62 which is selectively transmitted thereto through master valve 54, tube 66, passage 68 and bore 10. When the piston I2 is in the position illustrated in Fig. 2 the cylinder is loaded and when the piston is forced to the left by spring I4 the cylinder is unloaded." The piston I2 is provided with a rod 16 carrying a roller mechanism 18. A stationary cam 80 is associated with each liner 40. A ring 8| is slidably mounted upon the cylinder liner 40. A plurality of circumferentially spaced unloader pins 82 are fastened to the ring BI and extend longitudinally of liner 40 and are adapted to lift suction valve 52 so that the suction valve is continuously held in its open position. In such case gas entering the cylinder space through the suction valve is forced back into suction manifold 44. Since the discharge valve remains seated the net effect is an accomplishment of no useful work. Pins 82 are adapted to so'open suction valve 52 and unload the cylinder when the spring I4 moves the roller mechanism 18 to the left in Fig. 2 so that the roller mechanism climbs the cam and lifts ring 8I and pins 82.

In order to operate the master valve 64 and the unloading mechanisms there is provided an unloader control means 84 as described in Patent No. 2,185,473. The control means 84 is responsive to the suction pressure of the refrigerant existing within the compressor housing and is adapted to position the master valve 64 in accordance therewith to thereby selectively expose individual pistons I2 to the oil pressure capable of loading these cylinders.

When the system is at rest, the suction valves are held in open position due to the lack of oil pressure against the pistons I2 which means that the roller mechanism I8 will have climbed the incline of cam 80. When the motor is starting the reciprocation of the pistons will result in no compression being performed. However, as the motor reaches a higher speed and 'oil pressure is built up sufficient pressure will be available to load the compressor cylinders by movement of pistons I2. 7

Supplemental control mechanisms which form 'a part of my invention will control the delivery of oil to the pistons I2. Some of the cylinders of a multi-cylinder compressor in accordance with my invention are provided with a suction pressure responsive apparatus'designated by the numeral herein. The control means 84 previously discussed herein is adapted to cut off the supply of oil to pistons I2 and is responsive to low suction pressure thereby permitting individual cylinders to be unloaded when the suction pressure is low. The control means 90 is adapted to dump oil from bore I0 into the interior 46 of the compressor housing when the suction pressure becomes high. Control means 90 may be associated with some, though preferably not all, of the cylinders of a multi-cylinder compressor.

A restriction 69 is preferably provided in each passage 68 so that when oil is delivered to passage 68 by the master valve 64 then the restriction 89 will permit the dumping of oil by control means 90 or a valve means I2I to .be described herein to be efiective in lowering the pressure ahead of piston I2. Without the use of restriction 89 oil might be delivered sufiiciently fast to retract piston I2 even though som of the oil was being dumped.

The control means 90 comprises a housing 92 having a cylinder 94 therein and a bore 86 extending axially of the housing 92 through one end thereof. A valve element 98 is adapted to reciprocate in bore 98. Valve element 98 has an axial opening I00 extending therethrough which is exposed to the suction pressure existing in the interior 46 in th compressor housing. Legs I02 secure the valve element 98 to the end portion of a collapsible bellows I04. The other end of the bellows I04 is sealed by the top of the casing 92. A spring I06 is provided within the bellows I04 and adapted to react against an adjusting screw I08 threaded through the top of the casing 92. Adjustment of the screw I08 preselects the compression of spring I06. Spring I08 resists c01- lapsing of the bellows I04. Suction pressure transmitted from the interior 46 of the compressor through axial opening I00 to the cylinder 94 tends to compress bellows I04 thereby producing linear movement of piston element 98 in accordance with variations in suction pressure within the compressor. When the suction pressure is greatest the valve element 88 is moved inwardly in housing 02 and when the suction pressure is low spring I06 moves valve element 08 outwardly. Valve element 08 is provided with a pair of adjacent recessed portions H and H2 in its surface. A spring pressed ball detent H4 is adapted to enter recessed portion H0 or recessed portion II2 depending on the position of the valve element 08. A pin II 6 in housing 02 limits outward movement of valve element 38. Valve element 90 is therefore provided with a first extended position as shown in Fig. 3 when the suction pressure is low and a second retracted position when the suction pressure is high. A port I I8 provided in housing 32 adjacent the outer end of valve element 98 communicates with a chamber I and a passage I 22. The passage I22 is in fluid flow communication with bore 10 ahead of piston 12 as shown in Fig. 2. When valve element 00 is in the position shown in Fig. 3 the port I I0 is blocked thereby and the loaded or unloaded condition of the associated compressor cylinder is determined by means 84. However, when the suction pressure existing in the interior 46 of the compressor becomes excessive the bellows I04 is collapsed and the valve element 98 retracted until ball II4 drops into recessed portion II 2 therein. This provides a fluid flow communication from bore 10 through passage I 22, chamber I20, port H8 and bore 96 to the interior 46 of the compressor. vides a relief for any oil pressure attempting to act upon piston I2 to maintain the associated cylinder in a loaded condition. Since the dumping of the oil from bore 10 relieves all pressure on piston 12 except that provided by spring 14 the cylinder will be unloaded by means of pins 82 as previously describedherein. The control means 90 associated with difierent cylinders of the multi-cylinder compressor may be adjusted to be operative at different high suction pressures so that, for example, when a given suction pressure is obtained a certain cylinder is unloaded and when a still higher suction pressure is obtained an additional cylinder is unloaded and so on. Means are thus provided to prevent the operation of portions of the compressor when the suction pressure becomes sufficiently great to require a decrease in the volume of refrigerant handled to prevent overloading of motor I4. The control means 90 provides a means for determining which cylinders of a multi-cylinder compressor will be operative at high suction pressures.

The control means attempts to classify the optimum number of compressor cylinders corresponding to the suction pressures which may be encountered. However the classification is limited by the number of cylinders provided with control means 90 and although the optimum condition may be approached it is unlikely that it will be exactly obtained. Thus, instead of severely overloading the motor I4 it is probable that the overloading will be reduced to a relatively minor and usually harmless amount due to the operation of the control means 30 associated with various cylinders. However, even a slight overloading if maintained for a suflicient interval oi time could produce a gradual overheating of motor I4. The time during which the overloading occurs is determined by the load upon the evaporator of the refrigerating system. Therefore, even though means are provided to unload individual cylinders of the compressor when the suction pressure reaches predetermined values it is possible that the motor I4 could be overloaded.

This pro- I have found that the control means should be combined with an additional unloading mechanism preferably associated with other cylinders of the compressor and adapted to unload these other cylinders when the temperature of the motor I4 becomes excessive.

Fig. 4 illustrates the control which I desire to combine with control means 90. This control comprises a means to dump oil from bore I0 of certain of the compressor cylinders back through passa e I22 and chamber I20 to the interior 46 of the compressor housing. A temperature responsive valve I2I is secured to the housing of the motor I4. The usual field coil I23 of motor I4 is illustrated in Fig. 4 and it is the temperature thereof which will determine the operation of the valve I2I Valve I2I is connected by a line I24 to chamber I20 provided in compressor housing 20. The port I22 communicates with the bore I0 ahead of the most advanced position of piston 12. Line I24 delivers oil from bore 10 to valve I2I. A line I20 returns oil from valve I2 I to the interior 46 of the compressor housing 20. The valve I2I is provided with a hollow interior portion and a slidable element I30. The slidable element I30 is adapted for linear movement with in a guide I32. A port I34 operatively connects the interior of the valve I2I to the line I28. Slidable element I30 is adapted to selectively open and close port I34. The position of slidable element I30 is determined by the deformation of a bimetallic disk I36 located within valve mem- I2I in close proximity to field coil I23 of motor I4. A rod I 40 operatively connects bimetallic element I36 and slidable element I30. When the temperature of coil I23 becomes excessive bimetallic element I36 deflects to the right in Fig. 4 thereby opening port I34 and permitting oil to be dumped from bore I0 to the interior 46 of the compressor housing.

The fittings for control means 30 and valve means I2I are preferably interchangeable so that the same threaded opening I4I in the compressor housing may be either closed by a plug or have the control means 90 or valve means I2I asso-- ciated therewith.

It 'will be seen that I have provided a means for unloading compressor cylinders in response to high suction pressure and for unloading additional compressor cylinders in response to the maintenance of a high suction pressure for an abnormal length of time.

Although but one specific embodiment of the invention is herein shown and described, it will be understood that various changes may be made without departing from the spirit of the invention.

I claim:

1. A motor driven multi-cylinder compressor set having a first means for unloading individual cylinders thereof, fluid pressure means adapted to selectively overrule the action of said first means with respect to individual cylinders to load said individual cylinders under predetermined operating conditions, a mechanism associated with one of said cylinders and operable to relieve the eflect of said fluid pressure on said first means with respect to said one cylinder in response to excessive suction pressure in said compressor and a temperature responsive device including a valve associated with a second of said cylinders, said device being operable to open said valve to relieve the effect of said fluid pressure on said first means with respect to said second cylinder in response team excessive temperature of said motor.

cylinder when the compressor is at rest, fluid pressure creating means operating in unison with said compressor and creating suflicient pressure ata minimum speed to overcome said unloading means after the compressor has attained said minimum speed, a suction pressure responsive device comprising a valve associated with the unloading means of at least one of said cylinders, said valve having an open and a closed position, suction pressure responsive apparatus associated with said valve and adapted to open said valve when the pressure in said suction chamber exceeds a predetermined value, said valve when open being adapted to relieve the fluid pressure on the unloading means of said one cylinder, 9. motor temperature responsive device comprising a second valve associated with the unloading means of another of said cylinders, said second valve having an open and a closed position and a motor temperature responsive apparatus associated with said second valve and adapted to open said second valve when a predetermined temperature of said motor is exceeded, said second valve being adapted when open to relieve the fluid pressure on the unloading means of said last-mentioned cylinder. 1

3. A motor driven compressor set having a plurality of cylinders, means forming a common suction chamber, unloading means in conjunction with each cylinder operable to unload each cylinder when the compressor is'at rest, fluid pressure creating means operating in unison with said compressor and creating suflicient pressure at a minimum speed to overcome said unloading means after the compressor has attained said minimum speed and a suction pressure responsive device comprising a valve associated with the unloading means of at least one of said cylinders, said valve having an open and a closed position, and suction pressure responsive apparatus associated with said valve and adapted to open said valve when a predetermined suction pressure is exceeded in said compressor, said valve being adapted when open to relieve the fluid pressure on the unloading means of said one cylinder.

4. A motor driven compressor set having a plurality of cylinders, means forming a common suction chamber, unloading means in conjunction with each cylinder operable to unload each cylinder when the compressor is at rest, fluid pressure creating means operating in unison with said compressor and creating suflicient pressure at a minimum speed to overcome said unloading means after the compressor has attained said minimum speed, a master valve having an element movable to a plurality of stations and operable to selectively admit said fluid pressure to the unloading means ot individual cylinders in response to movement of said element to different stations, suction pressure responsive means to move said element to said stations in response to variations in the pressure in said suction chamber, a plurality of supplemental valves each associated with the unloading means of one of said cylinders, each supplemental valve having an open and a closed position and being operable when open to relieve the fluid pressure on the unloading means of its associated cylinder and means to open said supplemental valves in response to predetermined opterating conditions of said motor compressor se 5. A motor driven compressor et having a plurality of cylinders, means forming a common suction chamber, unloading means in conjunction with each cylinder operable to unload each cylinder when the compressor is at rest, fluid pressure creating means operating in unison with said compressor and creating sufllcient pressure at a minimum speed to overcome said unloading means after the compressor has attained said minimum speed, and a plurality of valves respectively associated with the unloading means of individual cylinders, each of said valves having an open and a closed position and having suct on pressure responsive apparatus associated therewith adapted to open its associated valve when a predetermined suction pressure is exceeded in said compressor, each of said valves being adapted when open to relieve the fluid pressure on the unloading means of its associated cylinder and each of said valves being provided with adjusting apparatus independent of the other valves by means of which the predetermined suction pressure at which each of said valves will open may be preselected.

CHARLES R. NEESON.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number 

